Cannot export C# project to HTML 5. Exports to Windows just fine.

[CaptainStack]

Godot version:
3.0.6

OS/device including version:
Windows 10 / Razer Blade (2017)

I've got the project set up and it exports fine to Windows. However, under Project -> Export I can't click the "Export Project" button.

When I click on the "Manage Export Templates" button, I'm prompted to install 3.0.6.stable.mono, which I download and install from the default mirror.

Unfortunately, this does not enable the "Export Project" button. Additionally, I get an error when from the main editor I attempt to "Run in Browser." It says "Could not open template for export."

I also posted this question on Stack Overflow:

https://stackoverflow.com/questions/51888631/how-do-i-on-windows-10-set-up-a-godot-project-to-be-developed-in-c-sharp-and-e

[CaptainStack]

Apparently C# -> HTML 5 is not supported yet:

#18364 (comment)